1. Field of the Invention
The present invention relates to a filter element of an element exposure type air cleaner built in an automobile engine or the like.
2. Description of the Related Art
Hitherto, the most generally used type of air cleaner provided in the intake system of an automobile engine has been the cover type in which the filter element is accommodated in an air cleaner case connected to an air intake duct. However, there is known the element exposure type of air cleaner in which the filter element, itself, is directly connected to the air intake duct, as optional parts or as the so-called replacement parts.
The filter element of the element exposure type has its filter element exposed to the outside, so that it has better air intake efficiency than the cover type air cleaner. This is effective in increasing the engine output, so that it is often used in, for example, sports cars as a replacement of the installed air cleaner. However, with the limited space in the engine room, it is necessary to take special care to manufacture the filter element into a proper shape.
FIG. 5 is a cross sectional view of one example of the aforementioned conventional element exposure type air cleaner unit. Filter element b is made of such a suitable filter material as paper, cloth, unwoven cloth, which is shaped into a tapered cylinder in which the filter wall face is pleated. A ring-shaped connecting member, d, which is made of synthetic resin and has an air intake duct connecting port c, is integrally connected to the larger diameter end portion side of the element b, while blind cover member e made of synthetic rubber is integrally connected to the smaller end portion side thereof. These members are adhered to their respective end portions by vulcanization. This air cleaner unit a is installed to the engine in the following way. The aforementioned air intake duct connection port is fitted and fixed to joint fixture h, which is connected by means of the connection duct g, and this duct g is connected to engine intake pipe f.
Only the outer peripheral portion of the blind cover member e of the aforementioned air cleaner unit a is formed into the shape of a ring from synthetic resin, while the inner periphery is formed by fixing such a cover member as a metal plate, or a synthetic resin plate.
In the conventional unit illustrated in FIG. 5, the air intake face of the filter element b is a tapered cylinder of a pleated filter material. This means that it occupies a small volume, so that a large air intake area can be achieved even if its external shape is made relatively compact. Therefore, this unit is designed so that a large amount of air can be taken in efficiently by forming the filter element into a shape occupying a small area.
However, in the filter element b of the air cleaner unit a of the conventional type, when air is sucked in from the filter wall face of the tapered cylinder, a turbulence occurs almost directly below the blind cover member e, which results in the production of a larger air intake noise. Accordingly, it has been pointed out that there is considerable loss air suction amount.